This guide addresses the effects of various types of pesticides on nontarget organisms, including natural enemies and beneficial organisms, such as honeybees, wildlife, fish, and nontarget plants.

Pesticides are an integral part of agriculture as Florida's climate fosters an environment conducive to major pest outbreaks throughout the entire year. Our environment also is favorable for the development and presence of beneficial organisms that positively affect our agricultural production and enhance our wildlife and plant communities. A side effect of usage of some pesticides results in unfortunate consequences to our nontarget organisms. Before making a pesticide application, it's important to become familiar with the area to be treated and the surroundings. Some pesticides are more "environmentally friendly" than others and may be selected for sites where there are special concerns.

Bees and Other Pollinators

Wild bees, certain wasps, honeybees, and other insects are important pollinating agents of crops (Figure 1). Some pesticides are harmful to these pollinators, causing direct losses of the insect populations and indirect losses of crop yield because of the lack of adequate pollination. The value of honey alone produced in Florida during 2012 was more than $23,000,000, according to the Florida Department of Agriculture and Consumer Services. Avoiding the use of materials that are toxic to these pollinators is the best method to enhance their survival. Pesticide labels, specifically with honeybees, will have statements in their "Environmental Hazards" section if there is a toxicity concern. For example, this statement was taken directly from a label:

Figure 1.

Many types of insects are important pollinators of crops.

Credit:

Frederick Fishel

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ENVIRONMENTAL HAZARDS

BEE CAUTION: MAY KILL HONEYBEES IN SUBSTANTIAL NUMBERS.

This product is highly toxic to bees exposed to direct treatment or residues on blooming crops or weeds. Do not apply this product or allow it to drift to blooming crops or weeds if bees are visiting the treatment area. Contact your local Cooperative Agricultural Extension Service or your local company representative for further information.

Methods to reduce exposure problems to bees include the following:

Do not apply pesticides that are toxic to bees during the plants' blooming period. Table 1 lists the active ingredients of pesticides that are highly toxic to honeybees. Only pesticides known to be registered in Florida are included in the table.

Select a product that is least toxic to bees.

As with any application, take precautions with drift.

Evening or night is the safest time of day for applications. Early morning would be fairly safe; midday has the greatest potential for toxicity concerns.

Move or cover beehives before using pesticides near hives.

Cooperate with beekeepers; notify them in advance of the application to give them a chance to move or cover their hives.

Beneficial Organisms

Beneficial organisms include various insects, mites, nematodes, fungi, bacteria, and other microorganisms that feed on or parasitize pest species (Figures 2 and 3). Some of these species are well-known and have been researched in Florida and other locations; however, many more are lesser-known species. The value of these organisms to agriculture and the environment are likely underestimated.

Figure 2.

Predatory spider.

Credit:

Frederick Fishel

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Figure 3.

Big-eyed bug feeding on aphids.

Credit:

Frederick Fishel

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Soil Microorganisms

Soil organisms are responsible for contributing to the decomposition of dead animal and plant material into organic matter, which is an important component of our soil fraction. Others are involved in the natural control of soil pests. Aside from their direct effects on pest organisms, soil microbes are a major agent in degrading pesticides. The breakdown of pesticides is beneficial from a crop rotation standpoint and for food residue concerns, and it also provides herbicide selectivity in some instances. The value of certain soil bacteria that have a symbiotic relationship with leguminous plants in fixing nitrogen translates into reduced synthetic nitrogen fertilizer inputs and increased crop yields. Because of this, the effect of soil-applied pesticides is usually short-lived. In fact, they may enhance the population of certain soil microorganisms in some instances.

Fish and Wildlife

The most obvious effects of pesticides on these organisms are direct effects of acute poisoning. At times, pesticides are solely blamed for fish kills. In many cases, however, the indirect effects of pesticides, such as causing dissolved oxygen depletion, are the reason for the kill (Figure 4). Pesticides can enter water sources through drift, runoff, soil erosion, leaching, and, occasionally, accidental or deliberate release (Figure 5). Table 1 lists pesticides that are classified as very highly or highly toxic to fish. Pesticides that range in concentrations of less than 0.1 to 1.0 ppm can kill fish. Pesticides can also kill birds in several ways, including direct ingestion of granules, baits, treated seeds, and direct exposure to sprays. Indirect bird kills may result from consumption of treated crops, contaminated water, or feeding on contaminated prey. Birds and other wildlife can be poisoned when baits, such as those targeting rodents, are improperly placed or not recovered in a timely fashion. Pellet and granular-formulated pesticides may be mistaken for food and consumed by birds and other wildlife. Table 1 lists pesticides that are classified as very highly to highly toxic to birds. These pesticides have bird acute oral LD50 values ranging from less than 10 to 50 mg/kg of body weight. Some pesticides have been implicated in negatively affecting the reproductive potential of certain birds and wildlife and have been banned. Certain practices can minimize harmful effects of pesticides on fish and wildlife:

Figure 4.

Many fish kills are caused by oxygen depletion rather than direct pesticide effects.

Credit:

Frederick Fishel

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Figure 5.

Fortunately, this is not a common sight in Florida.

Credit:

Frederick Fishel

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When given a choice of pesticides to control a certain pest, choose one that is relatively non-toxic towards fish and wildlife.

Labels of pesticide products have an "Environmental Hazards" section. This section lists special precautions and measures that should be taken to minimize harmful effects.

Treat only the areas needing treatment.

If possible, leave a buffer zone between bodies of water and treated areas.

If wildlife is present in a certain area, use precaution with placement of baits.

Plants and Phytotoxicity

Phytotoxicity refers to plant injury. Of all pesticide types as a group, herbicides are considered to have the greatest potential for causing phytotoxicity, since they are designed to control unwanted vegetation (Figure 6). Inert ingredients in pesticide formulations may also be capable of causing phytotoxicity.

Many species of plants in natural and undeveloped areas are desirable because they protect the watershed by reducing erosion and runoff. They also provide food and cover for wildlife and are part of an ecosystem's balance. A disruption of this balance may increase the likelihood of undesirable vegetation becoming more prevalent. There are situations where desirable plants are injured because of one or more of the following reasons:

Excessive application rate

Inadequate mixing and agitation

Environmental conditions, such as extremely hot temperatures and high humidity at the time of application

Plants which are under stress from lack of water and/or nutrients

Positive confirmation of phytotoxicity caused by pesticides can be difficult. Keeping accurate application records can assist in trying to determine if a pesticide is responsible for the suspected injury. Even with accurate records, pesticide injury can easily be confused with environmental disorders.

Figure 6.

Okra plants showing symptoms of herbicide injury.

Credit:

Frederick Fishel

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Summary

Very strict laws have been enacted to protect wildlife and other nontarget organisms; be aware of these (Figure 7). In many instances, following the directions on the pesticide label will prevent injury to nontarget organisms. When these directions are not followed, benefits from pesticides can be outweighed by the risks and harm associated with them.

Footnotes

1.

This document is PI-85, one of a series of the Agronomy Department, UF/IFAS Extension. Original publication date October 2005. Revised March 2014. Reviewed March 2014. Visit the EDIS website at http://edis.ifas.ufl.edu.

The use of trade names in this publication is solely for the purpose of providing specific information. UF/IFAS does not guarantee or warranty the products named, and references to them in this publication do not signify our approval to the exclusion of other products of suitable composition. Use pesticides safely. Read and follow directions on the manufacturer's label.

The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.